1. Field of the Invention
The present invention relates to a method of fabricating a display device, and more particularly, to a method of fabricating a display device using a flexible plastic substrate.
2. Discussion of the Related Art
Display devices typically include liquid crystal display (LCD) devices, plasma display panel (PDP) devices and organic electroluminescent display (OELD) devices. Recently, various display devices have been suggested to satisfy diverse users' need. Specifically, display devices having a light weight, a thin profile and a high efficiency and providing a full color moving image have been widely researched by virtue of enhancement and portability in utilization of information.
An electrophoretic display (EPD) device has been the subject of recent research due to its portability. Since the EPD device does not require a polarizing plate, a backlight unit and a liquid crystal layer, the fabrication cost of the EPD device is reduced.
FIG. 1 is a cross-sectional view showing an electrophoretic display device according to the related art.
In FIG. 1, an electrophoretic display device 1 includes first and second substrates 11 and 36 and an ink layer 57 between the first and second substrates 11 and 36. The ink layer 57 includes a plurality of capsules 63, and each capsule 63 includes a plurality of white pigments 59 and a plurality of black pigments 61. The plurality of white pigments 59 and the plurality of black pigments 61 are charged by condensation polymerization (polycondensation). For example, the plurality of white pigments 59 may be charged negatively and the plurality of black pigments 61 may be charged positively. The plurality of capsules 63 may have a uniform size through a filtering process. A plurality of pixel electrodes 28 connected to a plurality of thin film transistors (TFTs) (not shown) are formed on the first substrate 11. One of a positive voltage (+) and a negative voltage (−) is selectively supplied to each of the plurality of pixel electrodes 28 by the plurality of TFTs. The EPD device 1 utilizes an ambient light including a natural light and an indoor light as a light source, and the plurality of pixel electrodes 28 induce the movement of the plurality of white pigments 59 and the plurality of black pigments 61, thereby displaying images or texts.
When an electric field generated by the positive voltage (+) and the negative voltage (−) is applied to the ink layer 57, the plurality of white pigments 59 and the plurality of black pigments 61 move to the plurality of pixel electrodes 28 having an opposite polarity. For example, when the positive voltage (+) is applied to the plurality of pixel electrodes 28 in a pixel region, the plurality of white pigments 59 may move to the plurality pixel electrodes 28 and the plurality of black pigments 61 may move to the second substrate 36, thereby the pixel region displaying a black image. In addition, when the negative voltage (−) is applied to the plurality of pixel electrodes 28 in the pixel region, the plurality of black pigments 61 may move to the plurality of pixel electrodes 28 and the plurality of white pigments 59 may move to the second substrate 36, thereby the pixel region displaying a white image.
The EPD device 1 may be fabricated through an array process and a film deposition process. The plurality of TFTs and the plurality of pixel electrodes 28 are formed on the first substrate 11 through the array process, and an electrophoretic film (not shown) is attached to the first substrate having the plurality of TFTs and the plurality of pixel electrodes 28 through the film deposition process.
The EPD device may be widely used as an electronic book (e-book) or an electronic paper (e-paper) due to their low power consumption, light weight and thin profile. Specifically, when the EPD device is used as an e-paper, flexibility is required for portability. As a result, the EPD device includes a plastic substrate having a thickness of about 10 μm to about 200 μm as a base substrate for the purpose of maximizing the flexibility. Since the plastic substrate is too flexible to have a sufficient flatness on a stage during a fabrication process for the EPD device, the fabrication process is performed to the plastic substrate attached to an additional carrier substrate and the carrier substrate is removed after the fabrication process, thereby the EPD device completed.
FIGS. 2A to 2D are cross-sectional views showing a fabrication process of an array substrate for an electrophoretic display device according to the related art.
In FIG. 2A, an ablation layer 7 is formed on a carrier substrate 5 having a display area DA by depositing hydrogenated intrinsic amorphous silicon (a-Si:H). The carrier substrate 5 may be a glass substrate through which a laser beam can penetrate.
In FIG. 2B, a plastic substrate 11 is formed on the ablation layer 7 by sequentially coating and heating liquid plastics.
In FIG. 2C, a plurality of gate lines (not shown), a plurality of data lines 19, a thin film transistor (TFT) Tr and a pixel electrode 28 are formed on the plastic substrate 11. The plurality of gate lines cross the plurality of data lines 19, and the TFT Tr includes a gate electrode 14, a gate insulating layer 13, a semiconductor layer 18 including an active layer 18a and an ohmic contact layer 18b, a source electrode 20 and a drain electrode 22. In addition, the pixel electrode 28 is connected to the drain electrode 22.
In FIG. 2D, a laser beam LB from a laser apparatus 99 is irradiated onto an outer surface of the ablation layer 7 through the carrier substrate 5, and hydrogen (H), such as hydrogen gas erupts from the hydrogenated intrinsic amorphous silicon of the ablation layer 7. As a result, the plastic substrate 11 having the TFT Tr is detached from the carrier substrate 5.
Although not shown, a film deposition process is performed to the plastic substrate 11 detached from the carrier substrate 5. For example, an electrophoretic film including an ink layer and a common electrode may be attached to the plastic substrate having the TFT Tr and a protecting film may be attached to the electrophoretic film through the film deposition process, thereby an electrophoretic display (EPD) device is completed.
In the fabrication process for an EPD according to the related art, however, since the laser apparatus 99 having a relatively high price is used to detach the plastic substrate 11 from the carrier substrate 5, the fabrication cost for the EPD device increases. In addition, since it may take about 10 minutes to about 30 minutes to irradiate the whole carrier substrate 5 with the laser beam LB, the productivity is reduced. Further, since irradiation of the laser beam LB causes deterioration of the TFT Tr and break of the plurality of gate lines and the plurality of data lines 19, the production yield is reduced.